The PDI SS5000 Spring for Airsoft Bolt Action Rifles is now available at the X-Fire online store and is renowned as one of the most powerful spring series on the market. Originally developed for the Super 9 Pro, these springs are compatible with various bolt action rifles, including the APS-2, Type96, M40XB, and VSR-10. They feature a 13mm outer diameter and an 11mm inner diameter, requiring a 9mm spring guide and a piston with a 13mm inner diameter. Crafted from silicon chrome steel, these springs offer superior breaking strength and boast a finely tuned variable pitch design for light compression and rapid return.

According to them, unlike some "variable pitch" springs, PDI's springs are described as "perfect" variable pitch, ensuring comfortable cocking and consistent power. Because they are handcrafted, allowing for precise variable pitching that machines can't fully replicate, there might be a ±10% variation in power output. Users should also note that using a HI-SP cylinder kit might result in a slight decrease in output.